1. Field of the Invention
This invention relates generally to catheters and leads used in sensing electrical activity within a patient and administering therapy, and more particularly to such catheters and leads incorporating band electrodes configured for improved flexibility and tractability within the body.
2. Discussion of the Related Art
A variety of medical electrode catheters are available today for the diagnosis and treatment of various disorders of the cardiovascular and neurological systems. These electrode catheters can be used to sense electrical activity within the body and to deliver different forms of energy to stimulate, ablate, cauterize or pace. The core electrode technology common to all of these catheter designs is the application of one or more metallic bands on a catheter body. Examples of medical catheters using metallic banded electrodes include permanent and temporary cardiac pacing leads, electro-physiologic (EP) catheters, electrocautery probes and spinal stimulation catheters. The use of pre-formed metallic band electrodes manufactured from noble metals, such as gold or platinum and various other conductive alloys has found widespread application despite their functional design and performance limitations.
Metallic band electrodes possess distinct steerability problems. The steerability problems arise from the inflexible nature of the circular rings or bands. These inflexible bands of metal are typically adhesively bonded, crimped or otherwise attached to the exterior surface of the catheter or lead body. The bands are electrically coupled to electrical conductors that typically extend through one or more lumens in the catheter or lead body. The bands tend to be relatively thick and are therefore rigid. For neurological applications, the bands are typically about 3 millimeters wide. When it is considered that four or eight such ring electrodes are typically spaced about four millimeters apart along the distal end portion of the catheter body, they significantly impact the ability of the distal end portion of the catheter or lead to flex and conform to tissue structures.
As noted above, band electrodes placed on a flexible catheter or lead stiffen the catheter or lead and thereby reduce steerability. As such, catheters and leads having band electrodes are often restricted to applications where steerability and selective placement are not required. The steerability and placement problems of leads and catheters affect a variety of applications.
In cardiac therapies, such as for example ablation therapy, precise steerability and placement of a catheter is necessary. Ablation therapy requires that a catheter having sensing/ablation electrodes on the distal end is steered through the patient""s vascular system and into a predetermined chamber of the heart. The catheter is manipulated so as to place the electrodes into direct contact with the myocardial tissue that is sensed and/or to be ablated. The aberrant path and/or ectopic foci is first located using a mapping technique in which cardiac depolarization signals picked up by the electrodes are transmitted over electrical conductors in the lead to a suitable monitor/analyzer. Once located, the aberrant conductive pathway or the ectopic foci is ablated. This procedure requires the ability to precisely control the catheter over the surfaces of the heart. Therefore, a need exists for a catheter that provides precise control and steerability to accurately locate the electrodes in the heart.
In neurological therapies, such as for example neuromodulation, precise steerability and placement of a catheter is also necessary. Neuromodulation typically requires multi-electrode catheters be surgically implanted adjacent the spinal chord to stimulate the regions of the spinal cord that correspond to the regions of the body being treated. However, spinal cord stimulation has limited effectiveness for certain pain conditions. In many cases where spinal cord stimulation is inadequate, spinal nerves or peripheral nerves must be stimulated to provide relief from pain and other neurological conditions. However, with existing technology, spinal nerve or peripheral nerve stimulation cannot be accomplished without a surgical implant because appropriately sized leads having sufficiently steerability are unavailable. Surgical implants result in scarring and significant discomfort to the patient. Therefore, a need exists for a lead having enhanced steerability that provides greater specificity and increased accessibility to perform a broader array of nerve stimulation, while using less invasive methods to improve treatment outcome.
In addition, clinical studies have shown that spinal cord stimulation requires substantially more power to negate pain than direct stimulation of spinal or other peripheral nerve stimulation. For example, spinal cord stimulation typically requires the delivery of about 2 to 4 volts to effectively suppress pain whereas only about half or 1 to 2 volts need be delivered to spinal nerves or peripheral nerves to achieve the similar pain suppression. Higher energy requirements reduce battery life and, in turn, increase the frequency of surgery to replace the implanted battery-powered pulse generators. Therefore, a need exists for a neurostimulating lead that can be advanced to a location adjacent selected spinal nerve or peripheral nerve to reduce the energy requirements of neuromodulation.
The present invention meets the above needs and additional needs that will be recognized by those skilled in the art. The present invention provides a band electrode having increased flexibility. The present invention provides a method for manufacturing a lead having a high degree of steerability. The present invention provides a novel method for manufacturing a flexible band electrode and an electrical lead having a reduced diameter and at least one flexible electrode at or near the lead""s distal end. A lead manufactured in accordance with the present invention enables a novel neuromodulation method in which stimulating leads are percutaneously placed in the epidural space and advanced over a guidewire or using a stylet through a selected intervertebral foramen. In addition, upon review of the disclosure, those skilled in the art will recognize additional advantages and improvements conferred by the present invention.
The present invention provides a band electrode and a lead having a band electrode for a medical device and a method for manufacturing a band electrode. The band electrode including a conductive band having at least one slot cut through the conductive band to confer flexibility. The band electrode may be comprised of a conductive band having an outside diameter between about 2 French and about 12 French. The conductive band may be a material selected the group of platinum, gold, silver, platinum-iridium, stainless steel and MP35N or may be an alloy thereof. The lead for a medical device includes the band electrode as describe above and further includes a lead body having a conductor extending from a proximal end and a distal end of the lead body connected at one end to the band electrode. The lead body may have an outside diameter between about 2 French and about 12 French. The electrode and lead may be made by a method comprising providing a conductive cylindrical band and cutting at least one slot through the band to confer flexibility.